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powerpc/pseries, ps3: panic flush kernel messages before halting system

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Platforms with a panic handler that halts the system can have problems
getting kernel messages out, because the panic notifiers are called
before kernel/panic.c does its flushing of printk buffers an console
etc.

This was attempted to be solved with commit a3b2cb30f2 ("powerpc: Do
not call ppc_md.panic in fadump panic notifier"), but that wasn't the
right approach and caused other problems, and was reverted by commit
ab9dbf771f.

Instead, the powernv shutdown paths have already had a similar
problem, fixed by taking the message flushing sequence from
kernel/panic.c. That's a little bit ugly, but while we have the code
duplicated, it will work for this case as well. So have ppc panic
handlers do the same flushing before they terminate.

Without this patch, a qemu pseries_le_defconfig guest stops silently
when issued the nmi command when xmon is off and no crash dumpers
enabled. Afterwards, an oops is printed by each CPU as expected.

Fixes: ab9dbf771f ("Revert "powerpc: Do not call ppc_md.panic in fadump panic notifier"")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin
2017-12-24 02:49:23 +10:00
committed by Michael Ellerman
parent a08082f8e4
commit 35adacd6fc
5 changed files with 38 additions and 16 deletions
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24
arch/powerpc/kernel/traps.c
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@@ -39,6 +39,8 @@
#include <linux/ratelimit.h>
#include <linux/context_tracking.h>
#include <linux/smp.h>
#include <linux/console.h>
#include <linux/kmsg_dump.h>
#include <asm/emulated_ops.h>
#include <asm/pgtable.h>
@@ -143,6 +145,28 @@ static int die_owner = -1;
static unsigned int die_nest_count;
static int die_counter;
extern void panic_flush_kmsg_start(void)
{
/*
* These are mostly taken from kernel/panic.c, but tries to do
* relatively minimal work. Don't use delay functions (TB may
* be broken), don't crash dump (need to set a firmware log),
* don't run notifiers. We do want to get some information to
* Linux console.
*/
console_verbose();
bust_spinlocks(1);
}
extern void panic_flush_kmsg_end(void)
{
printk_safe_flush_on_panic();
kmsg_dump(KMSG_DUMP_PANIC);
bust_spinlocks(0);
debug_locks_off();
console_flush_on_panic();
}
static unsigned long oops_begin(struct pt_regs *regs)
{
int cpu;